1. Technical Field
The present invention relates in general to the field of circuit manufacturing and, more particularly, circuit manufacture using optical lasers.
2. Related Art
Circuit manufacture sometimes requires that a circuit be trimmed to meet certain specifications. Circuit trimming includes the removal of excess material from a circuit so that the circuit can perform more optimally. Trimming is sometimes accomplished using laser ablation. Laser ablation removes material from a spot by vaporizing the material at the spot using a laser beam.
Established techniques of circuit trimming include the use of q-switched lasers to produce laser pulses. A q-switched laser typically generates laser pulses having a duration of several nanoseconds and a repetition rate from a few hertz to approximately a few kilohertz.
A problem with trimming techniques of the prior art is a risk of thermal and/or photoelectric effects to material around the ablated spot. These effects may result in disturbances to the operation of the circuit being trimmed, particularly when the circuits include digital components. The possibility of these disturbances typically requires that digital circuits be reset after each ablation step to allow for accurate testing of circuit performance. Resetting of the circuit requires a time-consuming reinitialization of the circuit between each ablation step. For example, when the trimming disrupts a logic state required for testing of a digital circuit, it may be that signals must be sent to the digital circuit in order to bring it back to the required logic state. Because circuits may need to be trimmed and tested multiple times to optimize the total trimming, the times required for one or more reinitializations can significantly slow down the trimming process. Having to reinitialize the circuit may also adversely affect precision of the trimming process because there is an incentive to use fewer ablation steps, requiring fewer reinitializations, in order to complete trimming within a reasonable time. There is, therefore, a need for methods and systems of trimming circuits that allow for circuit testing without requiring that the circuit be reinitialized.